Hydraulic press



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HYDRAULIC PRESS Bertrand lapikse, Bexiey, Ohio, assignor to Birdshoro Steel Foundry and Machine Company, Birdsboro, Pa., a corporation of Delaware Application June 10, 1952, Serial No. 292,645

17 Claims. (Cl. 113-45) The present invention relates to hydraulic presses, and particularly to metal working presses such as drawing presses.

A purpose of the invention is to permit the use of a relatively light bolster plate on the main slide while providing adequate support, by making tthe main slide of hollow construction, suitably comprising a relatively heavy body, a relatively light bolster plate in spaced relation to the body and bolster-supporting posts connected to the body and to the bolster plate and distributed over the bolster plate. This construction permits location of the blank holder slide relatively close to the work, and shortens the members transmitting the load from the blank holder slide to the blank holder.

A further purpose is to make the main slide of box construction with an open interior, having posts, interconnecting a relatively heavy body and a relatively light bolster plate, and with sides and ends also interconnecting the body and the bolster plate.

A further purpose is to provide a blank holder slide in the space between the body and the bolster plate of the main slide, moving the blank holder slide with respect to the bolster plate, and where desired guiding the blank holder slide on certain of the posts which support the bolster plate from the body.

A further purpose is to extend relatively stifi stalks from the main shde in the direction of the crown, to guide the stalks both in the longitudinal and transverse horizontal directions on the crown, and to guide the main slide on housings extending between the crown and the base or bed of the press, so as to prevent distortion of the housings and the main slide and provide an inverted T- shaped guide for the main slide.

A further purpose is to employ one or more stalks extending outwardly (upwardly) from the main slide and guiding on the crown, with auxiliary guides of the main slide on the housings, in combination with a hollow main slide having a blank holder slide in the interior of the main slide and with posts supporting the bolster plate from the body of the main slide.

A further purpose is to construct the main slide from a body and separate front and back members, with interconnections between the body and the front and back members near the ends of the front and back members and a stalk or stalks extending toward the crown and secured at one end to a front or back member and at intermediate points to the body, the slide being guided by guiding the stalk or stalks and also by guiding the slide itself on the housings.

A further purpose is to provide cooperating openings between the body and the front and back members of the main slide and to interconnect by tension rods extending through the openings.

A further purpose is to locate a clevis in each of the front and back members and to engage the lower end of the stalk in the clevis by a pin.

A further purpose is to provide pads on the side of the bolster plate adjoining the blank holder slide which dis- States Patent tribute pressure between the bolster plate and the blank holder slide when the two come together.

A further purpose is to employ an auxiliary blank holder cylinder and ram, or a plurality of the same, acting between the main slide and the blank holder slide in order to absorb the shock when the main slide and blank holder slide move relatively toward one another into engagement.

A further purpose is to restrict the flow of hydraulic liquid from the auxiliary cylinder or cylinders to obtain a cushion effect.

A further purpose is to out 01f flow of hydraulic fluid from the auxiliary cylinder or cylinders by a valve or valves to make the blank holder slide retreat with the main slide in spaced relation thereto.

A further purpose is to trap hydraulic liquid in the blank holder cylinder or cylinders to stall upward movement of the blank holder slide and force the draw slide or main slide upward with respect to the stalled blank holder slide.

A further purpose is to release the stalling pressure in the auxiliary blank holder cylinders when chokes at the ends of the strokes have engaged for damping the possible dropping of the blank holder slide and then permitting final complete lifting of the blank holder slide together with the draw slide, as for stripping.

A further purpose is to employ a double acting pull back cylinder and ram on the main slide, with valve means controlling escape of hydraulic liquid from the pull back cylinder on the side from which the liquid is displaced when the main slide advances forward, with an automatic control put in action by the main slide for closing the valve means as the main slide advances toward the work, and desirably to utilize this application with a blank holder slide movable in the hollow of the main slide and at a proper time moving with the main slide.

A further purpose is to employ several blank holder cylinders and to interpose separate valves between the pump means and the blank holder cylinders, the valves being responsive in opening to drop in pressure in any individual blank holder cylinder to a level below that predetermined for that blank holder cylinder and in closing responsive to attainment of the predetermined pressure in an individual blank holder cylinder, the predetermined levels of pressure being difierent for the different blank holder cylinders.

A further purpose is to supplement the forward pressure of the main ram or rams by forward pressure exerted in double acting pull back cylinders.

A further purpose is to connect the main cylinders and the forward acting ends of the pull back cylinders to the pump means in succession, desirably locking the pressure in the pull back cylinders until the pressure in a succeeding main cylinder builds up to a predetermined value, and then desirably releasing the pressure in the pull back cylinders.

A furtherpurpose is to employ auxiliary blank holder cylinders and rams operating between the main slide and the blank holder slide to act as supporting columns to additionally support the blank holder slide at a plurality of points.

A further purpose is to energize the auxiliary blank holder cylinders to push the blank holder slide toward the Work as the main slide is withdrawn by the pull back cylinders.

A further purpose is to provide a throttled valve in connection with each auxiliary blank holder cylinder closed by relative approach of the main slide to the blank holder slide and throttle escape of hydraulic liquid from the auxiliary blank holder cylinders, the throttled valve preferably being of needle valve and orifice type.

A further purpose is to employ a relief valve upwardly connected to the blank holder cylinder when the main slide moves toward contact with the blank holder slide, so that the main slide can retract the blank holder slide.

A further purpose is to supply pressure to the cushion cylinders through a pressure control valve having a setting individual to each cushion, so as to permit the cushions to maintain different pressures.

A further purpose is to make up a closed hydraulic circuit between one or more of the cushioned cylinders and one or more of the blank holder cylinders, desirably using cylinders in which the efiective ram area at the cushion end of the closed circuit, equals the effective ram area at the blank holder cylinder end.

A further purpose is to interconnect one group of less than all of the blank holder cylinders (desirably one) at the end of which hydraulic liquid is displaced on movement toward the work to one group of lessthan all of the cushion cylinders (desirably one) at the end which causes movement away from the Work into a closed circuit, and interconnect another group of less than all the blank holder cylinders (desirably one) at the end of which hydraulic liquid is displaced on movement toward the Work to another group of less than all of the cushion cylinders (desirably one) at the end which causes movement away from the work, the efiective ram areas of blank holder cylinders and cushion cylinders in each closed circuit desirably being the same.

A further purpose is to interconnect one group of less than all the blank holder cylinders (desirably one) at the end at which hydraulic liquid is displaced on movement away from the work to one group of less than all of the cushion cylinders (desirably one) at the end which causes movement toward the work into a closed circuit, and to interconnect another group of less than all the blank holder cylinders (desirably one) at the end at which hydraulic liquid is displaced on movement away from the work to another group of less than all the cushion cylinders (desirably one) at the end which causes movement toward the work into a closed circuit, desirably having the same effective ram areas on the cushion cylinders and blank holder cylinders in each closed circuit.

A further purpose is to employ one cushion cylinder and one blank holder cylinder in each of the above groups.

- A further purpose is to guide the main slide in T formation, to mount the blank holder slide in the hollow of the main slide and in certain positions move the blank holder slide while it is in contact with the main slide, and to interconnect the respective blank holder cylinders and cushion cylinders in closed circuits so as to assure that the cushions will maintain the proper relation to the main slide and the blank holder slide.

A further purpose is to use the displacement of the rapidly lowering blank holder rams to measure the outward displacement of the cushion cylinders.

A further purpose is to use the displacement of the blank holder rams while lifting to control the locations of the lifting stroke of the cushions and produce the lifting for stripping action of the cushions.

A further purpose in triple action is to use the measuring feature for rapidly lowering the cushions in preparation for theupward draw stroke.

A further purpose is to provide the cushions with an outwardly acting pressing area independently of the cushion resistance area.

A further purpose is to make the cushions double actingand' to use both cushion areas when the cushions move down.

A further purpose is to decompress the hydraulic liquid in the cushions at the time that the main cylinder liquid is decompressed and before raising the main cylinder ram to avoid; the tendency of the cushion to creep due to the compressibility of the hydraulic liquid.

A further purpose is to place safety switches in a safety shut-off circuit and to make the switches act between the blank holder slide and the main slide so as to prevent operation of the press in case the parallelism of the blank holder slideand main slide is destroyed by distortion.

A further purpose is to obtain adequate protection against distortion of the various slides and related structure in very large hydraulic presses.

Further purposes appear in the specification and in the claims. r p

In the drawings 1 have chosen to illustrate a few only of the numerous embodiments in which my invention may appear, selecting the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure l is a fragmentary diagrammatic perspective partly in vertical section from frontto back, showing the novel construction of the main slide and blank holder slide and the tools employed in accordance with the present invention.

Figures 2 to 19 inclusive, illustrate a variation in the device of Figure 1, showing the preferred embodiment.

Figure 2 is a front elevation of'the preferred form, omitting structure in the lower right hand corner at the bottom of one of the tension rods. A portion of the front of the press is broken away to show the guiding of one of the stalks.

Figure 3 is a central vertical section of the press of Figure, 2, omitting the structure in the lower right hand corner, the section being taken on the line 3- -3 of Figure 4. The piping to the cushion rams has also been omitted.

Figure 4 is a top plan view of the device of Figure 2. Figure 5 is a plan section on the line 5-5 of Figure 3. Figure 6 is a plan section on the line 6-5 of Figure 3.

Figure 7 is a plan section on the line 7-7 of Figure 3,

but having the bottom bolster removed.

Figure 8 is a side elevation of the press of the invention, omitting a portion of the supporting structure under the bed. I v

Figure 9 is a vertical section on the line 9-9 of Figure 3, omitting structure in the lower right hand corner.

Figures 10 and 10 are portions of a single diagram matic view showing the hydraulic system employed in the preferred embodiment, Figure 10* showing the left hand part and Figure 1O showing the right hand part. Figure 10 is an enlarged fragment of Figure 10 Figure 11 is a diagrammatic central longitudinal sec? tion of valve 277, with one of the solenoids and one of the pilot valves shown in elevation.

I Figure ll is a diagrammatic central section of valve 170 with the solenoids and one pilot valve shown'in elevation.

Figure 12 is a diagrammatic longitudinal section of valve333. T p

Figure 13 is a diagrammatic central longitudinal section of valve 266 with the pilot valve shown in elevation and I the solenoid partially omitted.

Figure 14 is a diagrammatic centralsec'tion of valve 207 with the structure at one end shown in elevation.

Figure 14 is an enlarged diagrammatic central section of a variant form of control mechanism for the valve of Figure 14. The view' is turned in placement on the sheet.

Figure 15. is a diagrammatic central longitudinal section.

Figures 20 to 23 are block'diagrams showing. closed. hydraulic circuit connections between various groupings of blank holder cylinders and cushion cylinders.

In the drawings like numerals refer to like parts throughout.

Describing in illustration but not in limitation and referring to the drawings:

The hydraulic medium is generally referred to herein as hydraulic liquid, although it is sometimes designated as hydraulic fluid with similar meaning.

The need has existed particularly in the aircraft industry for metal forming presses such as deep drawing presses of larger load capacities than those heretofore generally available for such purposes. In many of these applications it is also desirable to have a very large press area. These requirements greatly increase the danger of distortion in normal press operation and especially in off center loading.

The present invention is designed primarily for deep drawing presses, but many of the principles involved are applicable to presses intended for other purposes. The preferred embodiment is being successfully applied to a press of 8000 tons capacity, effecting great savings in weight and space of operating parts over those which would be required with older designs.

In accordance with the invention, the main slide, often referred to as the draw slide, has been separated into a body of relatively heavy construction and a spaced bolster plate of relatively light construction and the'two spaced parts have been interconnected by posts distributed over the area of the main slide. This provides space between the bolster plate and the body in which the blank holder slide can be located, and in fact in some cases advantage is taken of the posts to guide the blank holder slide. The

box-like character of the main slide is completed by front and back and side members interconnecting the body and the bolster plate.

By the construction just described, it is possible to use comparatively short pressure pins to transmit the load from the blank holder slide to the blank holder, avoiding long pressure pins extending the full thickness of the main slide.

In order to guide the main slide, reliance is no longer placed upon guiding principally on tension rods or posts, which are likely to distort and cause distortion of cooperating parts of the stationary structure, and jam the slides. One or more relatively stiif stalks extend from the main slide, preferably at the front and back, and the main slide is guided by guides positioned on the lateral and also the longitudinal sides of the stalks at the crown, and also by auxiliary guides on the slide guiding on housings which extend between the crown and the base or bed. Thus the guiding of the main slide is of inverted T formation, giving ample protection against jamming of the main slide.

In some portions of the press cycle, the blank holder slide engages against pads on the side of the bolster plate remote from the work, and this assures uniform distribution of any forces acting between the main slide and the blank holder slide.

The main slide is desirably made up of a body and front and back members, which are joined together at the ends of the front and back members, suitably by tension rods extending through openings. The stalks desirably are connected at their ends to the front or back members and intermediate their ends to the body. The connection be tween the front and back members and the lower ends of the stalks is desirably accomplished by a clevis on the front or back member which is secured to the stalks by a pin extending through an opening in the stalk.

The tendency for impact to occur between the blank holder slide and the main slide is prevented by one or more auxiliary cylinders and rams acting between the blank holder slide and the main slide. Throttling devices in the auxiliary blank holder cylinders suitably become effective as the slides come close together. 7

In some phases of the operating cycles a valve is closed to cut off flow from each auxiliary cylinder so that the blank holder slide will retract with and in spaced relation to the main slide.

The pull back cylinders are desirably made double acting, and a very useful feature of the invention is the provision of valve means to control the escape of hydraulic liquid from the pull-back cylinders on the side from which liquid is displaced when the main slide advances, with an automatic control put in action by advance of the main slide for closing the valve means as the main slide advances toward the work.

The various blank holder cylinders are supplied with fluid pressure which is desirably set at a level individual for each blank holder cylinder. For this pur ose valves holder cylinder and each valve is responsive in opening to the drop in pressure in an individual blank holder cylinder to a level below that predetermined for that blank holder cylinder and in closing to attainment of the predetermined pressure in an individual blank holder cylinder, the predetermined levels or" the pressure being different for the different blank holder cylinders.

In a very large press of the character under discussion, I find it very desirable to use the upper areas of the double acting pull-back cylinders to supplement the main pressing cylinders to give a maximum of main pressure Where desired. The main pressure source is desirably connected in succession to the main cylinders and to the upper areas of the pull-back cylinders and preferably the pressure is locked in the pull-back cylinders until the pressure in a succeeding main cylinder builds up to a predetermined value and then the pressure in the pull-back cylinders may if desired be released.

For producing unusual parts, it is at times desirable to lock the hydraulic liquid in the auxiliary blank holder cylinders, according to the invention, so that the auxiliary blank holder cylinders will function as supporting columns for the blank holder slide.

in other sequences, when the main slide is being retracted, pressure may be applied to the blank holder cylinders, and release valves in the blank holder cylinders release liquid when the main slide in retraction forces the blank holder slide to retract. When, during this upward travel the main slide moves close to the blank holder slide a throttling device such as a needle valve, preferably, acts in the blank holder cylinder to provide a cushioning action.

In accordance with one aspect of the invention, the cushion cylinders are connected to the blank holder cylinders individually or in groups. The connection may be made from the end into which hydraulic liquid is displaced, on movement of the blank holder ram toward the work, to the cushion cylinder or cylinders, at the end which discharges liquid during movement away from the work for the purpose of controlling or measuring the downward displacement of the cushion cylinders during rapid lowering of the blank holder rams.

On the other hand the connection may be made from the blank holder cylinder or cylinders at the end from which hydraulic liquid is displaced on movement away from the work to the cushion cylinder or cylinders at the end which causes movement toward the work, so that the displacement of the blank holder rams while lifting will produce lifting and stripping by the cushion and will control or measure the lengths of the lifting strokes of the cushions.

In the preferred embodiment the blank holder ram area in each closed circuit will equal the cushion ram area, and in any case the two areas should have a predetermined relationship so that the movements of the blank holder slide and cushions will be interrelated as desired. Since an inverted T guide is provided for the main slide and since the blank holder slide in some portions of the stroke will often move with the main slide, the precision of this guiding is carried through the hydraulic interconnection from the blank holder cylinders to the cushions.

In some cases the measuring feature is used for rapidly lowering the cushions in preparation for the upward draw stroke in triple action, thus assuring that the cushions start the upward draw stroke from the proper positions.

The cushions have a downward pressing area independently of their resisting area which is very useful. When the cushions move, in some cases both of the pressure areas of the cushions will act, one for resisting and the other for measuring the permitted movement.

Thus the cushions not only perform the functions of resisting, but also travel downward by pressure on their pull-back areas, travel upward by pump action in triple action and travel upward by delivering hydraulic liquid in measured quantities to the blank holder cylinders in the corresponding closed circuits for retracting and stripping.

In order to avoid creeping of the cushions, the liquid in the cushions is decompressed at substantially the same time as that in the main slide'cylinders is decompressed.

The cushions will desirably have individual pressure settings and relief valves which function automatically when the cushion pressure rises above the predetermined level.

In order to guard against damage to the press in case of distortion as in grossly excessive off-center loading, switches are provided between the blank holder slide and the main slide which become effective on misalignment as to give a signal or render the press inoperative until the difiiculty is corrected.

Detailed description The general construction which may be employed in the present invention is illustrated generally in Figure 1, it being understood that Figure 1 shows certain desirable features with the elimination of mechanism which ap pears in the other form. Figure 1 is to be regarded as a diagrammatic showing, omitting the bed, the crown, the upright members, the hydraulic system and other structural parts of the press. It will be evident from the description that the principles there illustrated can be applied in a press without using the features of the hydraulic system later to be discussed.

As illustrated in Figure l, a bottom die 30 rests upon the bed of the press (not shown), and includes a female die forming portion 31, and a cushion pressure plate member 32, which is supported from the cushion (not shown in Figure l) by cushion pins 33 extending through openings 34 in the bottom die 30. The bottom die 30 has an upper clamping face 35 which cooperates with the clamping die, to be described later.

A main or draw slide 36 is preferably built up of composite elements, comprising a main body 37, side members 38 and a face plate or bolster 40. The face plate is spaced from the body to provide an inner recess 41, the whole being generally of box construction. Suitable interconnection of the side elements 38 with the body 37 is provided as by bolts 42, and the bolster is held in place on the side members by bolts 43.

It will be noted that the bolster 40 is of proportionately thin section, and the bolster is enabled to support the load due to widely distributed column supports provided by posts 44, which are interconnected as by threading at 45 into the draw slide main body 37, and are bolted at 46 to the bolster. It will be evident that the frequency of positioning of the posts in both directions may be varied to suit the requirements of load and other condi tions.

The bolster supports any suitable tooling, in this case illustrated as a male die 47 suitably secured to the bottom of the bolster by bolts 48. It will be understood that the male die 47 cooperates with the female die portion 31 and that any of a wide variety of forms of dies will be used depending upon the character of work which is being 8 formed, or the character of pressing operation performed, in case the press is not used for forming.

A blank holder slide 50 operates in the recess 41 provided at the interior of the main slide 36. The blank holder slide in this form guides on the posts 44, and openings are provided through the blank holder slide into which fit guiding bushings 51 engaging and sliding on some of the posts 44. In those locations where guiding is unnecessary, clearance is provided at 52 between the blank holder slide openings and the posts, it being understood that guiding bushings can be employed on as many posts as desired.

On the lower face of the blank holder slide,wear plates 53 are provided, suitably bolted to the blank holder slide at 54. It will be understood that the question of whether the wear plates are in several separate components or a single piece will depend upon the design and the size of the press. The wear plates are of course optional in the sense that they merely protect the face of the blank holder slide.

The wear plates have tapped openings which receive the threaded upper ends of blank holder pressure pins 55 which extend downwardly through openings 56 in the bolster. At the lower ends the blank holder pressure pins 55 are interconnected by bolted collars 57 and screws 57 with a blank holder die 58 which cooperates with the clamping face 35 on the lower die. It will be understood that the arrangement and positioning of the blank holder pressure pins 55 will depend upon the configuration of the blank holder die, and therefore upon the tooling of the particular work, the practice being to distribute the blank holder pressure pins endlessly around the punch with a spacing adequate to sustain the pressure and adequately support the blank holder die.

Where the blank holder die is of substantial width, as in the form shown, it is desirable to use one or more rows of blank holder pressure pins outside of the row which immediately surrounds the punch.

It will be understood that the construction of the blank holder slide and die with the interconnecting blank holder pressure pins permits the use of a relatively thin section of blank holder die in a heavy" press, so that you can perform a deeper draw operation within the daylight or working space limits of a particular press, since less of the working space is occupied by the blank holder dies, and the cost of the blank holder die is minimized.

It will be understood that the relatively thin bolster permits comparatively short blank holder slide pressure pins to be used, so that there is less danger of buckling the blank holder slide pressure pins. It will also be evident that the reduction of the thickness of the bolster represents an economy in manufacturing, and also reduces the cost of the side members 38, since they are only a portion of the supporting structure of the bolster, the balance of the loads being borne by the posts 44. It will also be evident that the side members are stressed essentially in compression only, since the bolster is no longer functioning as an arch as in prior practice.

The bolster will be provided with an overall distribution of blank holder pin holes, so that the bolster will conform to any desired tooling arrangement and therefore any desired location of the pressure pins.

The main or draw slide 36 in the form of Figure l is provided with stalks 60 at the front and back, which extend upwardly and toward their upper end (Figure 2) carry guides 127 which engage ways in the crown. will be understood that the stalk may be formed of a single element or fabricated of components as desired. In Figure 1 each stalk has a vertically extending stiffening rib 61, protruding toward the front or back of the press. 7

While the stalks as shown are at the front and back of the'draw slide, it will be understood that a single stalk, positioned for example in the center, may be used,

or that any other desired arrangement of the stalks may masses" 9 be employed, for example a plurality at the front and a plurality at the back.

Considering now the prefe. red embodiment of the invention as illustrated in Figures 2 to 9 inclusive, the press is mounted on bases 62 which support a bed 63 having a cushion opening 64 which contains a cushion 65 made up of four separate units 66. Each of the cushion units 66 comprises a cushion cylinder 67 cooperating with and engaging a cushion ram 68 which is upstanding from a yoke 70 anchored at opposite ends in the bed. The ram is of double acting construction as shown at the right in Figure 3, having a piston 71 and provided with bores 72 and 73 communicating respectively with the large and the auxiliary lowering areas of the piston.

As best seen in Figure 7, the upper portions of the individual cushion cylinders 67 have a rectangular configuration which engages guides 74 adjacent to the corners within the cushion opening 64 of the bed, and supported in some cases by separate plates or ribs 75 extending front to back across the cushion opening and forming an integral part of the bed.

The main or bottom bolster 76 is made in three sections, as best seen in Figure 3, the sections 77 and 78 at the sides resting directly on the front and back portions of thebed at 79.

The middle section of the bolster is depressed at the center to provide additional depth of section as shown in Figure 9 and rests upon the front and back portions of the bed at 31. The middle bolster section has cushion pin openings 82 through both the top and bottom sections of the bolster which receive the cushion pins 33 as already described in connection with Figure l. The cushion pins rest upon the upper pressure areas of the cushion cylinders.

In Figures 3 and 9 the lower die and cushion tooling are omitted for the sake of simplicity, but will rest directly upon the bolster, and may take the form shown in Figure 1.

As shown in Figure 9, stop rods 83 extend downwardly from the cushion cylinders through the yokes 70 and have limiting nuts 84 at the lower ends to prevent the cushion cylinders from rising beyond their limiting stroke in the upward direction. The nuts 84 move down with the stop rods 83 during downward travel of the respective cushion cylinders.

A crown 85 of the press is supported by housings 86 at the four corners, and the housings are aligned with respect to the bed and crown by keys 87. Tension rods 88 extend through the housings, and carry nuts 90 at the top and bottom. In order to provide prestressing of the tension rods, they are suitably heated before the nuts are preliminarily drawn up, and then prestressed by shrinkage. The heating can conveniently be accomplished by passing steam or other heating medium through openings 91 in the tension rods.

The crown is recessed at 32 (Figures 3 and 9) to provide space and mounting for main ram cylinders 93 (of which three are provided in the particular design shown). The main ram cylinders may have any desired distribution, but in the preferred form are in line along the center of the press. Main rams 94 are placed in cooperative relation in the main ram cylinders, and the main rams as a group are connected with the main 'or draw slide 36 at their lower ends. The main rams are recessed at 95 (Figure 9), and clips 96 are engaged in the recess and bolted to the draw slide.

The main ram cylinders are secured to the crown by bolts 97 at the top (Figures 3 and 4).

At the ends of the crown, pull-back cylinders 98 are positioned (two are provided in the preferred embodiment), and the pull-back cylinders contain cooperating rams 100 which have reduced diameters extending through the draw slide 36 and are held to the draw slide by nuts 101. The rams carry double acting pistons 102, one difrom blank holder cylinders 104 (of which six are shown in the preferred form), and the cylinders cooperate with blank holder rams 105 which are interconnected to the blank holder slide at their lower ends. The rams 105 carry single acting pistons 106 which cooperate with the cylinders. Heads 107 close the upper ends of the cylinders. The blank holder cylinders are bolted to the crown at 108 (Figure 3).

The blank holder slide has openings 110 (Figure 6) at intervals throughout the area, and posts 44 extend through the openings from the body 37 of the draw slide to the bolster 40, supporting the bolster in the manner described in connection with Figure 1. As in the form of Figure l, the bolster is of proportionally thin section.

The bolster has blank holder pressure pin openings 56 as described in Figure 1, and blank holder pressure pins pass through these openings as described in connection with Figure 1 (the blank holder die andthe blank holder pressure pins are omitted in the showing of Figures 2 to 9 for the purpose of clarity in illustration).

The bolster 40 has a series of pressure pads 111 (Figure 3) distributed over its upper surface, and permitting substantially uniform contact between wear plate 53 on the blank holder slide and the bolster 40. This wide area of contact is useful in permitting the pull-back cylinders to withdraw the blank holder slide along with the draw slide, and also in permitting the blank holder cylinders to apply supplemental pressure to the draw slide when operating on a single action cycle.

It will also be evident that a true bearing of the blank holder slide on the draw slide is important from the standpoint of obtaining uniformity of travel of the blank holder die during. the approach stroke and also of the cushions.

Preferably at the corners of the draw slide, auxiliary blank holder cylinders 112 are mounted on the draw slide,

and contain cooperating piston rods 113, which extend downwardly to and are bolted into the blank holder slide 50. The piston rods 113 carry pistons 113' (Figure 10 at the upper end, and are single acting, the lower ends only of the pistons being used.

The auxiliary blank holder cylinders 112 may desirably be employed as cushioning cylinders during the pullback stroke, to' prevent the draw slide, when moving upward, from bumping the blank holder slide which at that time will be substantially stationary.

For this purpose each of the auxiliary blank holder cylinders is provided with a hydraulic cushioning device of customary design, such as a choke 451 and a check valve 450 (Figure 10 to permit free return as later described.

The auxiliary blank holder cylinders may also be used to provide a hydraulic lock between the blank holder slide and the draw slide at a time on the retraction stroke when it is desired to have the draw slide and blank holder slides start their upward travels together. For this purpose it is merely necessary to trap oil below the piston of the auxiliary blank holder cylinders as later explained.

At the front and back of the draw slide, stalks 60 are mounted and extend upwardly into openings 114 in the crown. The stalks are essentially vertically elongated members, which may be fabricated in any suitable manner, although in the preferred embodiment they are castings of more or less I-bearn cross section with changing cross sectional dimensions. Each stalk is secured both to the draw slide body 37 and to one of the side members 38 by bolting at 115, 116 and 117 (Figures 2 and 9) to the draw slide body, and rests upon lugs 118 extending outwardly from the body. At the lower end of the stalk is connected by pin 120 into va clevis portion 121 of side member 38 of the draw slide. The bolting of the stalk to the body of the draw slide maintains a vertical alignment which can be corrected by shimming between the lugs and the stalk, whereas the pin engagement properly occurs at the bottom of the stalk and the side member. To aid in establishing a tight relation between the draw slide body and the side members, spacer blocks 122 (Figure 2) are interposed between the stalk 60 and the lugs 118.

The body of the draw slide is secured to the side members 38 at the corners by tie rods 123 which extend from lugs 124 on the body to lugs 125 on the side members.

The tie rods carry nuts 126 at the ends, and are preferably prestressed by heating and shrinking and are in addition, tightly fitted in the engaging holes 124' and 125 to act as shear pins to resist transverse forces.

Each stalk at the top carries adjustable guide shoes 127, adjustable in both forward and rearward, and right and left directions according to conventional gibb construction, which engage guideways 128, 130 and 131 respectively, which guide left and right and front and back respectively. The guideways extend from a point adjacent the bottom surface of the crown to a point even with or below the top of the crown and the guide shoes on the stalk are not required to extend above the top of the crown.

At the corner of the side members 38 of the draw slide, guides 132 are secured (Figures 2, which guide in both directions against guideways 133 and 134 on the housings 86. The guides are preferably of the conventional gibb construction, permitting accurate maintenance of guiding contact.

It will be evident therefore that the draw slide is guided at all four corners of each stalk at the top, and also at the four corners of the draw slide proper at the bottom, with relatively wide vertical spacing between the upper guiding and the lower guiding, so as to main-' tain great accuracy in vertical alignment. Since the stalks are located desirably at the front and back, it will also be understood that there is great accuracy in guiding against out-of-parallelism in a front-to-back relationship.

The blank holder slide, moving inside the draw slide, is guided by liners 135 between the vertically engaging surfaces of the draw slide and the blank holder slide for front-to-back relationship (Figure 6) and liners 136 similarly placed at the ends for right to left alignment. It will be evident that the guiding described for the .blank holder slide in the draw slide makes it unnecessary to guide the blank holder slide on the draw slide posts as described in Figure l, but that the guiding shown in Figure 6 is an alternate construction and optionally the guiding means of Figure 1 can supplement that of Figure 6.

'1' he two side members 38 of Figure 1 are in the form of Figures 2 to 9 carried into the space between the housings and beyond the housings at the end of the press and bolted together. at 137 and to the bolster at 138 (Figures 3 and 6).

Hydraulic system A suitable source of hydraulic fluid under pressure, desirably oil, is provided. in the preferred embodiment as illustrated in Figure invariable delivery pumps 14 3', 141 and 142 and variable delivery and reversible discharge purnp 143 are suitably driven as by motors 144 and 145. Suction oil is delivered to the pumps from suction tanks 146 and 147 through inlet connections not shown. The discharge from pumps 140, 141 and 142 takes place through valves 148, 150 and 151 (Figure lO which are preferably double solenoid and hydraulic pilot operated spring centered type as shown in detail in Figure ll except that plunger 3% is of regular commercial design to give the directions of How as described. The pilot pressure as shown by the dotted lines comes the press.

12 from a source 152 of pilot pressure at pump 143 and from sources 152' and 152 at pumps 163 and 142 through check valves 184', 185 and 184; The valves 148, and 151, when actuated by solenoids 153 connect through iines 148', 150 and 151 into line 582 and then through single solenoid hydraulic pilot operated and spring returned valve 154, to discharge through line 155 to con tribute at 161 to the performance of the downward operation of the press.

Valves 143, 150 and 151 if thrown in the opposite direction by solenoids 156 will deliver hydraulic liquid (oil) through check valves 157, 158 and 169 for the upward movement of the press.

The variable delivery pump 143 joins at 161 with the pump 163, driven by motor 164, connects at 167 through connection 165 and check valve 166 with the down stroke delivery of the other pumps after the latter have discharged through check valves 168 and 169. Pull-back delivery from variable pump 1&3 passes through double solenoid and hydraulic pilot operated spring centered valve 176 (Figure 10 shown in detail in Figure 11 and through check valve 171 to join the pull-back delivery of the other pumps at 172. From connection 172 the oil passes through solenoid and hydraulic pilot operated foot valve 173 (Figure 10 into connection 174 from which it branches into the two pull-back cylinders 98 at connections 1'75 and 176 (Figures 16 and 10 The foot valve as well known in the art embodies a free lifting check valve providing free flow in the direction from pump towards pull-back cylinders, with a solenoid and hydraulic pilot device added for pilot operating of the valve to permit unobstructed reverse flow of the oil. It is also equipped with a built-in relief valve to permit resistance flow in the reverse direction if the check valve is seated.

At 177 (Figure 10 the connection branches through needle flow control valve 178 and solenoid and hydraulic pilot operated and spring returned two-way valve 180 into return connection 181 (and 124), whereby hydraulic liquid is permitted to how into the overhead surge or quick prefill and exhaust tank 182 (Figures 10 and 10 This valve is opened during the rapid downward stroke of the press to permit accelerated closing of the press. The speed of the closing can be regulated by the setting of valve 178.

The pump 163 is further equipped with automatic compensating control 488 which automatically reduces the discharge of the pump to match the demand when maximum preset pressure has been developed at the down stroke discharge port of the pump, as well known. By use of single solenoid and hydraulic pilot operated and spring returned two-way valve 183 (Figure 10) this pressure compensatingfeature may be either connected or disconnected from the system.

Pumps 143 and 163 are each equipped with two built-in safety or maximum pressure relief valves (one for each direction of discharge) and these relief valves discharge into the suction connections of the pumps.

Pumps 14d, 141 and 142 have safety or maximum pressure relief valve protection through valves 186, 187 and 1% which have respective external returns to the suction tanks; The volumetric displacement of pump 143 may be adjusted by speed control stern 190 for controlling the downward speeds of the press or by adjusting control knob 191 for controlling the pull-back speed of These speed controls are well known in the art. Further speed control beyond the capacity of pump 143 is obtained by by-passing one or more of pumps 14-9, 3.41 and 142 by not energizing the respective solenoids of valves 148, 150 22rd 151, as these valves are designed to bypass the respective pump deliveries when placed in neutral position, at which time the hydraulic liquid will flow through connections 192, 193 and 194 into the respective suction tanks at 195 and 196.

The surge tank 132 is placed at the highest elevation in the system and receives the ma or portion of the hydraulic liquid discharged by the press during the return stroke. It is further provided with an overflow bafiie at 197 (Figure which permits return of excess hydraulic liquid from the surge tank into the suction tank at 198 and by means of connecting pipe 224. (below the liquid level) equal levels are automatically maintained in the two suction tanks. The surge tank 132 will then be filled to an adequate level to permit prefilling of the various press cylinders as needed during the rapid filling of the press.

During the rapid downward movement of the press the upper areas of the pull-back cylinders are filled by hydraulic liquid flowing under gravity through check valves 201 (Figures ll and 10 The two end blank holder cylinders are filled by hydraulic liquid flowing under gravity from the surge tank through pilot operated surge valves 202 (Figure 10 of well known character.

The four remaining blank holder cyl nders (two in ront and two in back) are filled by hydraulic liquid flowing under gravity through check valves 263, 294, 235 an 2%. The central main cylinder is prefilled by gravity hydraulic liquid from the surge tank by pilot operated surge valves 267 and 263 (Figure 10 and the remaining two main cylinders are likewise prefilled by hydraulic liquid flowing under gravity from the surge tank through surge valves 21% and 211. For further illustration of these surge valves see Figure.14.

The pilot operated surge valves 202, 207, 208, 219 and 211 are of the sliding piston type and are positively opened by hydraulic pilot pressure and at the proper interval in the cycle they are positively closed by hydraulic pilot pressure.

During the lifting of the press, these valves are opened by hydraulic pilot pressure, therefore permitting free return of hydraulic liquid from the cylinders to the surge tank. The return of hydraulic liquid from the upper portions of the pull-back cylinders takes place via connections 212 (Figure 10 and 213 (Figure 10") through single solenoid and hydraulic pilot operated lapped piston type spring returned valve 432 (Figure 10 and via check valve 215 and single solenoid and hydraulic pilot operated foot valve type spring closed two-way 216 (Figure 10) (which is held closed by hydraulic line pressure and spring pressure combined; it is allowed to open by low system pressure when the hydraulic closing pressure is released).

Line 217 serves as an equalizing line for uniform return flow through the valves 432 and 216. Valve 216 fulfills essentially the same function as valve 432 except that its relief valve portion protects the connected portion of the system against excessive pressure in case of over-pressure due to valve failure as Well known. The valves 432 and 216 are well known in the art.

One of the four front and rear blank holder cylinders is discharged to the surge tank through connections 296, 237, 295 (Figure 10 224 (Figure 10 and 221 (Figure 10 into double solenoid hydraulic pilot operated and spring centered four-way valve 222 (described more fully in connection with Figure 11). When deenergized this valve is in its neutral position and permits flow from connection 221 to connection 223 and 224 into the surge tank (Figure 10 Valves, 222, 225, 226 and 227 are identical in their design and functions. The other three of the four front and back blank holder cylinders discharge into the surge tank respectively through connections 287, 228, 286, 234, 235, valve 226, connections 236 to connections 223 and 224; also through connections 292, 233, 291, 230,

231, valve 225, connection 232 to connections 223 and 224; also through collections 282, 218, 281, 238, 240, valve 227, connection 241 into connections 223 and 224.

Variable pump 143 has a built-in solenoid operated automatic control for selecting the volumetric delivery of the pump, embodying two solenoids and a spring centering device so arranged that three distinct settings can be obtained, as well known in the art, namely full preset return volume, full preset pressing volume, and an intermediate partial pressing volume. By selecting the desired settings the pump is not only capable of lowering and raising the slides of the press at selected speed, but in addition permits a selection of pressing speed independent of the rapid closing speed. During the idling time when the press is not in use but the motors are operating, the minimum delivery of the pump towards pressing is by-passed through single solenoid hydraulic pilot operated spring returned two-Way valve 242. When deenergized this valve by-pass delivery from connection 161 through valve 242 and connection 244 into suction tank 146 (Figure 10').

After the press has been closed rapidly to a predetermined level, a limit switch 435 is tripped whereby valve 173 is closed, causing trapping of hydraulic liquid in the lower portions of pull-back cylinders 98, thereby causing decelerating of the downward movement of the draw and blank holder slides simultaneously.

Pumps 140, 141, 142 and 143 and pump 163 will now discharge simultaneously through connections 167 and 247 (Figure 18 thence through the respective connections 248, 250, 251, 252, 253 and 254 for delivering pressure hydraulic liquid to the six blank holder cylinders.

From connection 248 hydraulic liquid will flow through check valve 255, connection 256, two-way valve 257 (later described in connection with Figure 13) and connection 253 to surge valve 282 into which it is connected by ports 260 and 261. Port 260 is blocked While port 261 connects into a hydraulic pilot cylinder. Valve 261' (Figure 10 which is of single solenoid and hydraulic pilot operated two-way foot valve type as Well known has been closed at this time, thus preventing escape of pressure via check valve 262 and passages 263 and 264 (Figures 10 and 10 Hence operating pressure will be generated at port 261, causing the shifting and closing of the valve plunger in valve 202. The motion of this valve plunger causes opening of the valve port at 260, thereby permitting entry of hydraulic liquid into the blank holder cylinder which is connected to valve 202.

A duplicate function takes place from connection 254 through check valve 265, two-way valve 266, connection 267 into ports 268 and 270 with pressure escape prevented through check valve 271 and passage 272 by the same valve 261' which is closed in this position, and in this case pressure on port 276 will cause shifting of the valve plunger in connected surge valve 202, permitting entry of pressure fiuid from port 268 into the connected blank holder cylinder, thus causing downward travel of the blank holder slide by pressure on these blank holder cylinders, while the draw slide is forced to descend with the blank holder slide until contact is made between the blank holder die and the work which is placed upon the lower die.

The other four blank holder cylinders receive pressure in like fashion from connections 250, 251, 252 and 253 through check valves 271, 272, 273 and 274 respectively, thence through two-way valves 275, 276, 277 and 278 respectively (later described in relation to Figure 13), and connections 2%, 281, 218, 232 to cylinder 284. connections 285, 286, 228 and 237 into cylinder 288, connections 2%, 291, 233, 292 into cylinder 293, also through connections 294, 295, 237 and 296 into cylinder 297. At this time side connections 220, 230, 

